SLC2A1 and gestational diabetes: Consistently, immunohistochemistry (IHC) staining confirmed that GLUT1 expression was increased in both syncytiotrophoblasts (STBs) and interstitial extravillous trophoblasts (iEVTs) in GDM placentas when compared to the control group, a finding further verified by immunofluorescence (IF) staining that demonstrated abundant GLUT1 presence in trophoblast cells (Fig. 1D, Supplement 1A).